ISSN:
1573-6881
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Chemistry and Pharmacology
,
Physics
Notes:
Abstract 1. The number ofp-chloromercuribenzoate (PCMB)-reactive sulfhydryl groups per molecule was estimated to be 2 in cytochrome oxidase based on a mininum molecular weight of 69,300 daltons [12] or about 3.2 based on a minimum molecular weight of 110,000 [10]. 2. The number of SH groups titrated in cytochrome oxidase with PCMB or with AgNO3 was the same in the absence of sodium dodecyl sulfate (SDS), while in the presence of SDS additional SH groups became available to AgNO3, but not to PCMB. 3. Removal of most of the intrinsic copper of cytochrome oxidase with ≥0.01 M NaCN (followed by passage through Sephadex G-25 to remove the copper cyanide and the excess cyanide) exposed approximately 1.5 or 2.4 additional SH groups per molecule to PCMB depending on the minimum molecular weight of the enzyme. 4. A determination of the heme of cytochrome oxidase by formation of the pyridine hemochrome revealed the same heme content as was obtained with Δɛ 605 nm (reduced minus oxidized)=7.6×103 cm−1 (g atom Fe)−1. 5. Repeated freezing and thawing or freeze-drying was found to be detrimental to this preparation of cytochrome oxidase. However, the SH groups decreased or became unavailable to PCMB approximately in direct proportion to the decrease in the heme groups.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01516209
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